"As we've seen around the world in recent years, social media can be a major forum for terrorist sentiment and activity. This will be a vital tool to screen out terrorists, public safety threats, and other dangerous individuals from gaining immigration benefits and setting foot on US soil."

President Donald Trump, an avid fan of social media site Twitter, controversially issued an order two years ago to have "extreme vetting" put in place. The new social media policy kicked in on Friday.

The Hill reports for now, only details for "major social media websites" will be required, without specifying which.

Before Friday, extreme vetting was only applied to visa applicants who'd been to countries with a major terrorist presence.

Rights group the ACLU described the policy as "another ineffective and deeply problematic Trump administration plan" that would "infringe on the rights of immigrants and US citizens by chilling freedom of speech and association".

It's estimated more than 14 million travellers to the United States, including those there for study and work - will be affected. There will reportedly only be exemptions for a few types of visa and diplomats.